Can I ask your opinion in relation to neutral /earth on this rather untidy changeover arrangement located just downstream of the main isolator? There are 2no 3-pole contractors with mains in bottom left and generator in bottom right. On the stud adjacent they have connected gen neutral, DNO neutral and installation earth. The arrangement means a self-imposed conversion to an unauthorised TNCS. I can’t be sure if the existing supply is already TNCS.
However, it seems to me that any given code should be accompanied by a clear indication of the reasons the call has been made along with a reference to at least the most pertinent regulation that has been breached.
The first bit's easy - reg 463.1.4 demands the switching of all live conductors - so certainly a non-compliace with BS 7671 (not 'just' unlawful under the ESQCR).
(I can see that 551.6.2 doesn't make the situation entirely clear though)
551.6.1 reads to me as if the contactors need to be rated for isolation too (I can't tell from the picture whether those do) - so perhaps something more to check there.
Certainly undesirable to have N currents flowing in protective conductors - but I guess we've all seen long standing N-PE faults in the pre-RCD days not to fear that the sky will fall as a result. Unless there was a particularly small c.p.c. between the DNO supply and this N-PE link, I'd be tempted by a C3 (but with an additional note about contravening the ESQCR).
Edit - I've just seen Graham's concern about diverted N currents - that's a good point and could well justify a higher code.
However, it seems to me that any given code should be accompanied by a clear indication of the reasons the call has been made along with a reference to at least the most pertinent regulation that has been breached.
The first bit's easy - reg 463.1.4 demands the switching of all live conductors - so certainly a non-compliace with BS 7671 (not 'just' unlawful under the ESQCR).
(I can see that 551.6.2 doesn't make the situation entirely clear though)
551.6.1 reads to me as if the contactors need to be rated for isolation too (I can't tell from the picture whether those do) - so perhaps something more to check there.
Certainly undesirable to have N currents flowing in protective conductors - but I guess we've all seen long standing N-PE faults in the pre-RCD days not to fear that the sky will fall as a result. Unless there was a particularly small c.p.c. between the DNO supply and this N-PE link, I'd be tempted by a C3 (but with an additional note about contravening the ESQCR).
Edit - I've just seen Graham's concern about diverted N currents - that's a good point and could well justify a higher code.
